1. Field of the Invention
The present invention is generally related to a propulsion system for a marine vessel and, more particularly, to a trim system that is automatically actuated as a function of the speed of the marine vessel.
2. Description of the Related Art
Those skilled in the art of marine propulsion devices and marine vessels are familiar with many different ways to control the trim angle of a marine propulsion device. The operational position of a marine vessel relative to the water is affected by several parameters. These include the trim angle of the marine propulsion device, such as an outboard motor, the angle of trim tabs if the marine vessel is equipped with trim tabs, and the speed of the marine vessel relative to the body of water in which it is operated. A preferred embodiment of the present invention is related to the trim angle of the marine propulsion device.
Those skilled in the art of marine propulsion and marine vessels are familiar with many different ways in which the marine propulsion device, such as an outboard motor or stemdrive unit, can be moved to affect its angular position relative to the marine vessel.
U.S. Pat. No. 4,565,528, which issued to Nakase on Jan. 21, 1986, describes a tilting mechanism for a marine propulsion device. Several embodiments of trim and tilt arrangements for outboard drives that adjust the trim condition of the outboard drive unit in response to drive thrust and/or velocity of the boat so as to provide the optimum flow resistance under all conditions are described.
U.S. Pat. No. 4,861,292, which issued to Griffiths et al. on Aug. 29, 1989, discloses a speed optimizing positioning system for a marine drive unit. A system for optimizing the speed of a boat at a particular throttle setting utilizes sensed speed changes to vary the boat drive unit position vertically and to vary the drive unit trim position. The measurement of boat speed before and after an incremental change in vertical position or trim is used in conjunction with a selected minimum speed change increment to effect subsequent alternate control strategies. Depending on the relative difference in before and after speeds, the system will automatically continue incremental movement of the drive unit in the same direction, hold the drive unit in its present position, or move the drive unit an incremental amount in the opposite direction to its minimum position. The alternate control strategies minimize the effects of initial incremental movement in the wrong direction, eliminate excessive position hunting by the system, and minimize drive unit repositioning which has little or no practical effect on speed.
U.S. Pat. No. 4,931,025, which issued to Torigai et al. on Jun. 5, 1990, describes a posture control device for a marine vessel. A number of embodiments of watercraft propulsion unit controls for optimizing watercraft performance and maintaining stability are described. Performance is optimized in the illustrated embodiments by adjusting the trim angle of the propulsion device and stability is maintained by changing either the trim condition or the speed of the propulsion unit. The desired posture may either be preset in response to an earlier stable condition or may be set upon reaching of optimum performance.
U.S. Pat. No. 4,939,660, which issued to Newman et al. on Jul. 3, 1990, discloses a fuel conserving cruise system for a marine drive unit. A system for optimizing the operating efficiency of a boat by balancing fuel consumption against cruising speed utilizes a comparison between engine speed and boat speed to effect automatic positioning of the drive unit. The measurements of boat and engine speed before and after an incremental change in vertical position or trim position are used to calculate the percent changes in boat speed and engine speed which, in turn, are used in conjunction with selected minimum and maximum incremental percentages to effect subsequent alternate control strategies.
U.S. Pat. No. 5,352,137, which issued to Iwai et al. on Oct. 4, 1994, describes an automatic position controller for marine propulsion systems. Several embodiments of automatic position controls for marine propulsion devices, wherein the lift condition of the propulsion device is adjusted in response to a sensed running condition of the watercraft such as changes in acceleration, speed or planing condition, are described.
U.S. Pat. No. 5,366,393, which issued to Uenage et al. on Nov. 22, 1994, describes an automatic trim controller for marine propulsion units. Several embodiments of automatic trim controls for marine outboard drives for maintaining the optimum trim angle under all running conditions are described.
U.S. Pat. No. 6,997,763, which issued to Kaji on Feb. 14, 2006, describes a running control device. The device sets an optimum trim angle automatically. The running control device includes a propulsion force control section that controls the propulsion force of the propulsion device. The running control device also includes a tilt angle control section that controls the tilt angle of the propulsion device.
The patents described above are hereby expressly incorporated by reference in the description of the present invention.
Those skilled in the art of marine vessel propulsion and control are familiar with many different ways in which the trim angle of a marine propulsion device can be used to change the operating characteristics of the vessel. In addition to many different types of automatic trim control systems, many manual trim control systems are known to those skilled in the art. In typical operation, the operator of a marine vessel can change the trim angle of the associated propulsion units as the velocity of the vessel changes. This is done to maintain an appropriate angle of the vessel on the water as it achieves a planing speed and as it increases its velocity over the water while on plane. It would be beneficial if a system could be provided that performs the trim operation automatically, as a direct function of vessel speed, without requiring intervention by the operator of the marine vessel. The change in trim angle of the propulsion unit, if automatically performed, would enhance the operation of the marine vessel as it achieves planing speed and as it further increases its velocity over the water while on plane.